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Effect of 13 weeks of subchronic exposure to TCDD, PeCDF, PCB126, PCB153 and PCB126/PCB153 on hepatic gene expression

ABSTRACT: This study investigates the effects of the aryl hydrocarbon receptor (AhR) ligands TCDD, PCB126 and PeCDF; the non-AhR ligand PCB153 and the binary mixture PCB126/PCB153 on hepatic gene expression in female sprague dawley rats. Rats were treated with toxicological equivalent doses of TCDD (100ng/kg), PeCDF (200ng/kg), PCB126 (1000ng/kg) and PCB153 (1000ug/kg) 5 days a week for 13 weeks. Keywords: Environmental pollutant toxicity comparison

ORGANISM(S): Rattus norvegicus

PROVIDER: GSE5789 | GEO | 2006/09/08

SECONDARY ACCESSION(S): PRJNA97147

REPOSITORIES: GEO

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Project description:The dioxin congener 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) causes a wide range of toxic effects in rodent species, all of which are mediated by a ligand-dependent transcription-factor, the aryl hydrocarbon receptor (AHR). The Han/Wistar (Kuopio) (H/W) strain shows exceptional resistance to many TCDD-induced toxicities; the LD50 of >9600 µg/kg for H/W rats is higher than for any other wild-type mammal known. We have previously shown that this resistance primarily results from H/W rats expressing a variant AHR isoform that has a substantial portion of the AHR transactivation domain deleted. Despite this large deletion, H/W rats are not entirely refractory to the effects of TCDD; the variant AHR in these animals remains fully competent to up-regulate well-known dioxin-inducible genes. TCDD-sensitive (Long-Evans, L-E) and resistant (H/W) rats were treated with either corn-oil (with or without feed-restriction) or 100 µg/kg TCDD for either four or ten days. Hepatic transcriptional profiling was done using microarrays, and was validated by RT-PCR analysis of 41 genes. . A core set of genes was altered in both strains at all time points tested, including CYP1A1, CYP1A2, CYP1B1, Nqo1, Aldh3a1, Tiparp, Exoc3, and Inmt. Outside this core, the strains differed significantly in the breadth of response: three-fold more genes were altered in L-E than H/W rats. At ten days almost all expressed genes were dysregulated in L-E rats, likely reflecting emerging toxic responses. Far fewer genes were affected by feed-restriction, suggesting that only a minority of the TCDD-induced changes are secondary to the wasting syndrome. Rats from sensitive (Long-Evans, LE) and resistant (Han/Wistar, HW) strains were treated with 100 ug/kg TCDD or corn oil vehicle and sacrificed either 4 or 10 days after treatment. LE control rats were either fed normally or feed-restricted to control for the wasting effects of TCDD treatment. Each treatment group contains four or five animals (biological replicates), each of which was assayed on an individual microarray.

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Effect of 13 weeks of subchronic exposure to TCDD, PeCDF, PCB126, PCB153 and PCB126/PCB153 on hepatic gene expression

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